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"Landscapes are essential to the quality of life in California…."
"Landscape design, installation, and maintenance can and should be water efficient" (Excerpts from: Title 7, Div. 1, Ch. 3, Article 10.8 (d) and (e) of the Government Code)
The California State Legislature recognizes the importance of landscaping for recreation, fire protection, erosion control, enhancing environmental conditions and replacing ecosystems in areas of development. However, California faces a real challenge to meet the water needs of a growing population with a limited supply of water. To meet this challenge, water use in landscapes must become more efficient. There are many ways to accomplish this goal and even modest improvements can have a cumulative effect in saving a great deal of water.

New Methods for Landscape Area Measurement- November 9, 2011
DWR hosted this webinar to provide information on new methods and techniques for measuring landscape area. Click here to watch the recording of this meeting.

Landscape Water Use Conservation Methods

There are many methods that can reduce the amount of water used in a landscape and still maintain the health, appearance and function of the landscape. Here are just a few:
  • Regular maintenance of irrigation systems
  • Regular adjustment of irrigation controllers
  • Education of residents, customers and employees regarding the importance of efficient water use
  • Irrigation scheduling based on plant water needs
  • Preventing overspray, irrigation runoff and low head drainage
  • Water-efficient landscape designs using low water-use plants
  • Efficient irrigation systems
  • Minimize amenity turf areas
  • Soil improvements and mulch
  • Scheduling irrigation during early or late hours
  • Water budgeting using evapotranspiration data from CIMIS and crop coefficients from "WUCOLS" -Water Use Classification of Landscape Species
  • Dedicated landscape water meters or submeters for monitoring of water budget and leak detection
  • Conformance to local or the State Water Efficient Landscape Ordinance
  • Coordinate efforts with local water agency for incentives, rebates and planning programs

Landscape Water Use Conservation Technology

ET Irrigation Controllers
There are several new types of irrigation controllers that base the irrigation schedule on evapotranspiration data. Some of the controllers use historical data only. Others use a combination of historical data and real-time data feeds from on-site temperature sensors, sunlight intensity indicators or from complete weather stations. These "ET" controllers represent a new frontier in scheduling irrigation by enabling the irrigator to apply the amount of water estimated to be required by the landscape plants. This is a great improvement over irrigating an arbitrary "run time" when the amount of water needed and the amount of water applied is usually not matched. The advantages of using an ET controller include: reduced run-off, less damage to pavement, fences and buildings: increased health of plants from fewer diseases and insect pests and better air circulation in the soil, fewer "soggy" or dry areas, lower water bills, and reduced energy costs. ET based controllers have been used in large turf areas such as golf courses and parks for some time. Newer models are being used and tested for use by residential customers throughout the state. The Bureau of Reclamation has posted a literature review of water saving studies for weather and soil moisture based landscape irrigation devices.

Landscape Water Use Frequently Asked Questions

What is WUCOLS?

Answer: WUCOLS stands for Water Use Classifications of Landscape Species. It is a University of California Cooperative Extension Publication. The project was developed by the San Francisco and San Mateo County Office in cooperation with 32 landscape professionals. This project was initiated and funded by DWR. The purpose and intended use is to provide guidance to landscape professionals when selecting plant material, while taking into consideration water needs. It also serves as a guide to assist in developing irrigation schedules for existing landscapes. The Landscape Coefficient Method and WUCOLS are combined in the publication called: A Guide to Estimating Irrigation Water Needs of Landscape Plantings in California.

Is there a specific law governing the landscape water in California?

Answer: Yes. Assembly Bill 1881 (2006) required all local agencies to adopt a water efficient landscape ordinance by January 1, 2010. DWR's Model Water Efficient Landscape Ordinance reflects the State policy of promoting the conservation and efficient use of water in landscapes.

What are the objectives of DWR's Model Water Efficient Landscape Ordinance?

Answer: The objectives, consistent with AB 1881 are:

  • To promote the values and benefits of landscapes while recognizing the need to invest water and other resources as efficiently as possible.
  • To establish a structure for planning, designing, installing maintaining and managing water efficient landscapes in new and rehabilitated projects.
  • To establish provisions for water management practices and water waste prevention for established landscapes.
  • Use water efficiently without waste by setting a Maximum Applied Water Allowance (MAWA) as an upper limit for water use and reduce water use to the lowest practical amount.

How can I get help with landscape water use calculations when submitting a landscape design package to the city or county?

Answer: DWR offers an online calculator for determining the MAWA and ETWU for a landscape project and DWR's Model Water Efficient Landscape Ordinance has examples of specific calculations, including:

  • Calculation of the Maximum Applied Water Allowance (MAWA)
  • Calculation of the Estimated Applied Water Use (ETWU)

Where can I get evapotranspiration rates to calculate the Maximum Applied Water Allowance (MAWA)?

Answer: Reference evapotranspiration values are available in Appendix A of the MWELO. DWR's CIMIS Reference Evapotranspiration (ETo) data may be used in the MAWA and ETWU calculations. CIMIS ETo data is available for many locations in California. A water budget calculator is available at:

www.water.ca.gov/wateruseefficiency/landscapeordinance/.

What does CIMIS ETo mean?

Answer: CIMIS stands for California Irrigation Management Information System. It is a program unit that manages a network of over 140 automated weather stations throughout California for the purpose of estimating ETo. ETo stands for reference evapotranspiration. It is an estimate of the amount of water used by water evaporated from both soil and grass surfaces and the amount used by well-irrigated grass (transpiration). It is calculated from the weather data measured on site and retrieved daily by a central computer in Sacramento using complex sets of equations. CIMIS also provides daily ETo maps at 2-km grids by coupling remotely sensed satellite data with point measurements at individual CIMIS stations. For more information on the ETo maps, please refer to wwwcimis.water.ca.gov/cimis/cimiSatSpatialCimis.jsp.

See also the DWR White Paper: Evapotranspiration Adjustment Factor

I'm in landscaping and I need CIMIS ETo information. What is the cost of obtaining it?

Answer: The CIMIS information is free.

Should I rely solely on CIMIS ETo data, landscape coefficients, and the available water holding capacity of soils to schedule my irrigations?

Answer: No. Irrigation scheduling will rely heavily on the experience of the person responsible for the landscape design and/or maintenance. It also relies on estimates for water use, such as CIMIS ETo data, as well as soil moisture monitoring devices (rainfall sensors), which all contribute to accurate and efficient irrigation scheduling.

How can I attend a landscape water audit class?

Answer: In California Landscape irrigation auditing classes are offered by several USEPA WaterSense Labeled programs:

Has the California Building Standards Commission approved the revised California Graywater Standards?

Answer: The Graywater Standards for non-residential applications are currently undergoing revision by the CBSC.

Is there information available regarding the use of gray water for residential landscape in California?

Answer: Yes. The Department of Housing and Community Development recently updated the graywater standards for residential applications.

Where can I find technical information about the use of recycled water for landscape purposes in California?

Answer: Please visit the Recycling and Desalination Web Page.

The brochure "Recycled Water Use in Landscapes" contains basic information regarding irrigating with recycled water.